This study is designed to test the hypothesis that the occurrence of catastrophic extrarenal complications of E. coli-related Hemolytic Uremic Syndrome (HUS) and the severity of the associated acute renal failure are the result of ongoing gastrointestinal absorbtion of Shiga-like toxins (SLTs) and subsequent cytokine activation during the course of disease. Early treatment with Synsorb PK, an agent designed to bind SLTs in the intestine and to prevent their continued entry into the systemic circulation, will decrease patient mortality and reduce the incidence of serious adverse events.